JP4046029B2 - Method for manufacturing transistor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transistor manufacturing technique.
[0002]
[Prior art]
In the manufacturing process of a semiconductor device, it is extremely important to flatten the surface of the film in order to prevent disconnection or short circuit of wirings formed thereon. In particular, in a transistor, since the uniformity of the thickness of the gate insulating film greatly affects the electrical characteristics, a technique for forming the gate insulating film more flatly is required.
Conventionally, a gate insulating film of a transistor has been mainly formed by a CVD method (see Patent Documents 1 and 2).
[0003]
[Patent Document 1]
JP-A-8-181325
[Patent Document 2]
JP 10-144929 A
[0004]
[Problems to be solved by the invention]
However, conventional transistors have problems such as insufficient gate breakdown voltage and increased leakage current. This is mainly due to the coverage of the CVD film with respect to the unevenness of the substrate surface. For example, in a top-gate transistor, since the gate insulating film is formed on a patterned silicon film (semiconductor film), a step due to at least the thickness of the semiconductor film itself is formed on the substrate. In the patterning process of the semiconductor film, silicon oxide and silicon nitride, which are the underlying insulating films, are also partially etched, so that a step corresponding to the etching amount is further formed on the substrate. These are superposed to form a larger step. If a gate insulating film is formed on such a step portion by CVD, a thin portion of the gate insulating film is formed at the upper end portion or side end portion of the semiconductor film, causing problems such as a decrease in gate breakdown voltage and an increase in leakage current. .
[0005]
In addition, foreign substances such as particles may be generated in the CVD method, which may cause a further decrease in gate breakdown voltage, an increase in leakage current, or a short defect between the gate electrode and the source or drain.
The present invention has been made to solve the above-described problems, and a transistor manufacturing method capable of manufacturing a transistor having excellent electrical characteristics and high reliability, and an electro-optical device including the transistor The purpose is to provide electronic equipment.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a transistor manufacturing method of the present invention includes a step of forming a semiconductor film on a substrate, a step of patterning the semiconductor film into an island shape, and a gate insulating film on the semiconductor film. And a step of forming a gate electrode on the gate insulating film, wherein the step of forming the gate insulating film comprises applying a first insulating film constituting at least a part of the gate insulating film. In the patterning step of the semiconductor film, the physical properties of the coating liquid used in the first insulating film forming step, the coating conditions, and the required film thickness of the first insulating film are included. Accordingly, the pattern size of the semiconductor film is set accordingly.
[0007]
In this method, since the first insulating film is the coating film, a step due to the film thickness of the semiconductor film itself, a step due to the base insulating film removed in the patterning step, or the like can be planarized by the first insulating film. . Thereby, the uniformity of the film thickness of the gate insulating film is increased, and a transistor with a high breakdown voltage and a small leakage current is obtained. Further, in the coating method, foreign matters such as particles are not generated, so that the reliability of the transistor is increased.
[0008]
Note that in the first insulating film formation step, various coating methods such as a spin coating method, a dip coating method, a roll coating method, a curtain coating method, a spray method, and a droplet discharge method (inkjet method) can be used. However, in the spin coating method in particular, since the liquid film spreads in the substrate surface by centrifugal force, a flatter film can be easily formed.
As the coating solution, a raw material for the first insulating film, a precursor thereof, or various liquid materials that can be converted into the first insulating film by heat treatment can be used. Specifically, a high-quality gate insulating film is formed by using a solution obtained by dissolving polysilazane, SOG (Spin On Glass) or the like in a solvent such as xylene as a coating liquid, and converting it into silicon oxide by heat treatment. be able to. In particular, polysilazane can form an insulating film having higher resistance to cracking and less residual impurities than other materials. The heat treatment of polysilazane is WET O ₂ It is desirable to carry out in an atmosphere (oxygen atmosphere containing water vapor). Accordingly, the nitrogen component in the insulating film that causes polarization can be reduced, and the electrical characteristics of the transistor are stabilized.
[0009]
By the way, in the formation process of the first insulating film, the flow resistance of the coating liquid may vary due to the unevenness of the substrate. For example, in the region where the semiconductor film is formed, the flow resistance of the coating liquid is relatively larger than in other regions, and the film surface of this portion may be raised. The size of the swell is not only the thickness of the coating film (that is, the thickness of the first insulating film), the physical properties of the coating liquid (viscosity, etc.), the coating conditions, but also the semiconductor film on which the coating film is formed. It depends on the size. In other words, the film thickness uniformity of the gate insulating film is closely related not only to the process of forming the first insulating film but also to the patterning process of the semiconductor film as the previous process. In the patterning process of the semiconductor film, it is desirable that the pattern size is optimally set in advance according to the physical properties of the coating liquid used in the subsequent process, the coating conditions, and the required thickness of the first insulating film. .
[0010]
As a specific procedure, first, the overall size of the semiconductor film and the film thickness of the gate insulating film are determined according to the required performance of the transistor. Next, the required thickness of the first insulating film is determined according to the thickness of the gate insulating film, and the physical properties (viscosity, etc.) of the coating solution and the coating conditions are determined so as to obtain this thickness. If these conditions are determined, the maximum size of the semiconductor film is determined from, for example, experimental data, so that the film surface of the coating film does not swell or is allowed to swell. In this case, the pattern size of the semiconductor film may be set. For example, when the entire size of the semiconductor film is larger than the maximum size, the semiconductor film may be divided into a plurality of parts. In this manner, by making the transistor a multi-gate structure and reducing the size of each semiconductor film (that is, not more than the above maximum size), the gate insulating film formed thereon can be further planarized.
[0011]
In the step of forming the gate insulating film, a step of forming a second insulating film constituting a part of the gate insulating film by subjecting the semiconductor film to surface oxidation before the step of forming the first insulating film. It is desirable to provide In the transistor, in addition to the film quality and film thickness uniformity of the gate insulating film, the interface characteristics of the gate insulating film greatly affect the electrical characteristics of the transistor. Therefore, by providing a surface oxide film that provides better interface characteristics than the first insulating film, which is a coating film, at the interface with the semiconductor film, high performance of the transistor can be achieved.
[0012]
As a method for forming the second insulating film, for example, there is a method in which the surface of the semiconductor film is plasma-treated using an oxygen-containing gas as a processing gas. Alternatively, the semiconductor film may be heated in an ozone gas atmosphere. In this method, ozone is decomposed in the vicinity of the heated semiconductor film, and oxygen radicals are generated. Then, the surface of the semiconductor film is oxidized by oxygen radicals in an active state, and an oxide film is formed. For this reason, it is possible to obtain a high quality interface with less damage on the film surface than the method using plasma, and to simplify the apparatus and shorten the processing time.
[0013]
Further, the step of forming the gate insulating film may include a step of forming a third insulating film constituting a part of the gate insulating film by an evaporation method at an interface with the semiconductor film or an interface with the gate electrode. Good. This also provides good interface characteristics. Note that the third insulating film may be formed only on either the interface with the semiconductor film or the interface with the gate electrode, but can also be formed on both.
According to another aspect of the invention, an electro-optical device includes the transistor manufactured by the above-described method. The electronic apparatus according to the present invention includes the electro-optical device. Thereby, a high-performance electro-optical device and electronic apparatus can be provided.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a liquid crystal device as an example of the electro-optical device of the invention will be described with reference to the drawings. In all the drawings below, the film thicknesses and dimensional ratios of the constituent elements are appropriately changed in order to make the drawings easy to see.
[0015]
As shown in FIG. 1, the liquid crystal device 1 of this embodiment includes an active matrix substrate 10, a counter substrate 20, and a liquid crystal layer 40 as a light modulation layer held between the substrates 10 and 20. .
[0016]
FIG. 1A is a diagram illustrating a planar structure of a main part of the active matrix substrate 10.
The substrate 10 is provided with a plurality of scanning lines 33 and signal lines 34 in the X direction and the Y direction on a substrate body 10A made of glass, plastic, or the like, and is partitioned by these wirings 33 and 34. A pixel electrode 14 is disposed in each pixel. Each pixel is provided with a plurality (two in this embodiment) of TFTs (thin film transistors) 30 for performing energization control of the pixel electrode 14. That is, in the vicinity of the intersection of the scanning line 33 and the signal line 34, two island-shaped semiconductor films 31 are provided along the signal line 34, and a common gate electrode 33 a is provided so as to cover both the semiconductor films 31. Is arranged. The gate electrode 33a is provided so as to branch from the scanning line 33 toward the preceding scanning line side. The region of the semiconductor film 31 facing the gate electrode 33a functions as a channel portion, and the positions facing left and right across the channel portion are a source portion and a drain portion, respectively. The source portion of each semiconductor film 31 is conductively connected to the signal line 34 via the contact hole 12a, and the drain portion is conductively connected to the pixel electrode 14 via the contact holes 12b and 13a.
[0017]
FIG.1 (b) is a figure which shows the structure of the AA 'cross section of Fig.1 (a).
The TFT 30 of this embodiment has a top gate type structure, and a semiconductor film 31, a gate insulating film 32, and a gate electrode 33a are stacked in this order from the lower layer side of the substrate 10A serving as a main body. That is, a gate insulating film 32 is provided on the semiconductor film 31 provided in an island shape on the base insulating film 11 so as to cover the entire surface of the substrate, and is opposed to the semiconductor film 31 on the gate insulating film 32. A gate electrode 33a is provided. An interlayer insulating film 12 is provided on the substrate 10A so as to cover the gate insulating film 32 and the gate electrode 33a, and a signal line 34 and an intermediate layer 35 are provided on the insulating film 12. The insulating film 12 is provided with a contact hole 12a that communicates with the source part 31b of the semiconductor film 31 and a contact hole 12b that communicates with the drain part 31c, and the signal lines 34, The intermediate layer 35 is electrically connected to the source part 31b and the drain part 31c, respectively. Further, an interlayer insulating film 13 is provided on the substrate 10A so as to cover the interlayer insulating film 12, the signal line 34, and the intermediate layer 35, and the pixel electrode 14 is provided on the insulating film 13. The substrate configured as described above is further provided with an alignment film 15 made of polyimide or the like so as to cover the pixel electrode 14 and the interlayer insulating film 13.
[0018]
On the other hand, the counter substrate 20 is provided with a translucent common electrode 24 made of ITO or the like on a substrate body 20A made of a translucent substrate such as glass or plastic. An alignment film 25 is provided.
[0019]
By the way, the gate insulating film 32 described above has a two-layer structure of an insulating film 32a covering the surface of the island-shaped semiconductor film 31 and an insulating film 32b stacked thereon. The insulating film 32a is obtained by forming silicon oxide, silicon nitride, or the like by a vapor deposition method such as PECVD method or sputtering method. Alternatively, the surface of the semiconductor film 31 may be oxidized. Examples of this method include a method in which the surface of the semiconductor film 31 is subjected to plasma processing using an oxygen-containing gas as a processing gas, and a method in which the semiconductor film is irradiated with ultraviolet rays in an oxygen-containing gas atmosphere. In any of these methods, a good interface can be formed with the semiconductor film 31, which contributes to higher performance of the transistor. In the present embodiment, as a method of forming the insulating film 32a, a method of surface oxidation by ultraviolet irradiation is employed.
[0020]
On the other hand, the insulating film 32b is formed by applying a raw material of this insulating film, a precursor thereof, or a material in which a material that can be converted into an insulating film by heat treatment is dissolved in a solvent, and applying this onto a substrate. Has been.
As this coating solution, for example, polysilazane (which is a general term for polymers having Si—N bonds) can be used. Polysilazane is mixed with a liquid such as xylene and applied onto the substrate, and converted to silicon oxide by heat treatment in an atmosphere containing water vapor or oxygen. One of the polysilazanes is [SiH ₂ NH] _n (N is a positive integer) and is called polyperhydrosilazane. This product is commercially available from Tonen Corporation under the product name “Tonen Polysilazane”. In addition, [SiH ₂ NH] _n When H in the inside is substituted with an alkyl group (for example, a methyl group, an ethyl group, etc.), it becomes an organic polysilazane and may be distinguished from an inorganic polysilazane.
[0021]
Further, SOG (Spin On Glass) can also be used as a liquid that becomes an insulating film by heat treatment after being applied. This SOG is a polymer having a siloxane bond as a basic structure, and includes an organic SOG having an alkyl group and an inorganic SOG having no alkyl group, and alcohol or the like is used as a solvent. The SOG film is used as an interlayer insulating film of LSI for the purpose of planarization. The organic SOG film is easily etched with respect to the oxygen plasma treatment, and the inorganic SOG film has a problem that cracks are easily generated even with a film thickness of several hundred nm. For this reason, it is rarely used as an interlayer insulating film or the like in a single layer, and is used as a planarizing layer on the upper layer of the CVD insulating film. In this respect, polysilazane has high crack resistance and oxygen plasma resistance, and even a single layer can be used as a thick insulating film to some extent. Polysilazane can form a high-quality insulating film with fewer residual impurities than other materials. Therefore, in this example, a mixture of polysilazane and xylene is used as the coating solution.
[0022]
As a coating method, various methods such as a spin coating method, a dip coating method, a roll coating method, a curtain coating method, a spray method, or a droplet discharge method (ink jet method) can be used. In particular, in the spin coating method, since the coating liquid is formed by being stretched in the substrate surface by centrifugal force, a more uniform film is easily formed. For this reason, in this example, a spin coat method is used as a coating method.
When a part of the gate insulating film 32 is formed by the coating method in this way, the insulating film 32b is formed flat so as to level the unevenness of the substrate surface due to the fluidity of the coating solution, and the gate in the region where the semiconductor film 31 is formed. The film thickness uniformity of the insulating film 32 is higher than the conventional film formed by the CVD method.
[0023]
However, in the coating method, since the flow resistance of the coating solution changes depending on the unevenness of the substrate surface, there may be some unevenness in the film thickness. That is, since the insulating film 32b is formed so as to have a level difference caused by the patterning of the semiconductor film 31, as shown in FIG. 8A, the film of the coating film M is formed in the formation region E1 of the semiconductor film 31 that becomes the level difference. The thickness L2 is thinner than the film thickness L1 of the coating film M in the non-formation region E2 of the semiconductor film 31, and the flow resistance of the coating liquid is relatively increased accordingly. Therefore, when the difference in flow resistance between the regions E1 and E2 is large or when the step surface is wide, as shown in FIG. 8B, the film surface of the insulating film 32b is formed in the formation region E1 of the semiconductor film 31. A large swell g occurs, which hinders the operation of the transistor. Therefore, it is necessary to keep the film thickness non-uniformity of the insulating film 32b within a certain range. The bulge of the film surface is the film thickness of the coating film M formed in each region E1, E2. In addition to the difference (L1-L2), the physical properties of the coating liquid (viscosity, etc.), the coating conditions, and the size W of the semiconductor film 31, the insulating film 32b, which is a subsequent process, is formed in the patterning process of the semiconductor film 31. The pattern size must be optimally set according to the physical properties of the coating liquid used in the process, coating conditions, and the required film thickness of the insulating film 32b.
[0024]
As a specific manufacturing procedure, as shown in FIG. 2, first, a semiconductor film is formed on the entire surface of the substrate (step S1; semiconductor film forming step), and then this semiconductor film is patterned to form each pixel. An island-shaped semiconductor film is formed on the substrate (semiconductor film patterning step).
[0025]
At this time, first, the overall size of the semiconductor film disposed in one pixel and the thickness of the gate insulating film are determined based on the required performance of the transistor (step S2). Next, the required thickness of the insulating film 32b is determined according to the thickness of the gate insulating film, and the physical properties and coating conditions of the coating solution are determined so as to obtain this thickness (step S3). If such conditions are determined, for example, experimental data or the like determines the maximum size of the semiconductor film that does not swell on the film surface of the coating film, or is allowed to be swelled. For example, if the overall size of the semiconductor film is not larger than the maximum size, this overall size is used as the pattern size of the semiconductor film as it is, and when the overall size is larger than the maximum size, it is within one pixel. The semiconductor film is divided into a plurality of parts to reduce the pattern size of each semiconductor film. Thus, the number and pattern size of the semiconductor films arranged in one pixel are determined (step S5), and the semiconductor film formed in step S1 is actually patterned (step S6).
[0026]
Thereafter, the surface of the semiconductor film 31 patterned in step S6 is oxidized to form an insulating film 32a (step S7; second insulating film forming step). Further, a coating method is applied on the insulating film 32a. The insulating film 32b is formed (step S8; first insulating film forming step). Then, a transistor is manufactured by patterning the gate electrode 33a on the gate insulating film 32 thus formed (step S9; gate electrode forming step).
[0027]
Hereinafter, these steps will be described in detail with reference to FIGS.
First, as shown in FIG. 3, a base insulating film 11 made of a silicon oxide film is formed on a substrate body 10A made of glass or the like by plasma CVD using TEOS (tetraethoxysilane) or oxygen gas as a raw material. . In addition to the silicon oxide film, a silicon nitride film or a silicon oxynitride film may be provided as the base insulating film. The base insulating film 11 is intended to condition the surface state of the substrate 10A and prevent contamination of the semiconductor film 31 due to impurities in the substrate 10A, but this may be omitted.
[0028]
Next, a semiconductor film made of an amorphous silicon film is formed on the base insulating film 11 using a plasma CVD method or the like. The semiconductor film is not limited to an amorphous silicon film, and may be a semiconductor film including an amorphous structure such as a microcrystalline semiconductor film. Alternatively, a compound semiconductor film including an amorphous structure such as an amorphous silicon germanium film may be used. Subsequently, the semiconductor film is subjected to a crystallization process such as a laser annealing method or a rapid heating method (such as a lamp annealing method or a thermal annealing method) to crystallize the semiconductor film into a polysilicon film (formation of a semiconductor film). Process). In the laser annealing method, for example, a line beam having a long beam length of 400 mm is used with an excimer laser, and the output intensity is, for example, 400 mJ / cm. ² And Note that the second harmonic or the third harmonic of the YAG laser may be used. With respect to the line beam, it is preferable to scan the line beam so that a portion corresponding to 90% of the peak value of the laser intensity in the short dimension direction overlaps each region.
[0029]
Next, as shown in FIG. 4, the semiconductor film 310 is patterned to a desired size (semiconductor film patterning step). At this time, in order to form a film with good flatness in the formation process of the insulating film 32b as the next process, the pattern size of the semiconductor film 310 is limited within a certain range in accordance with the above-described procedure. For example, in this example, in order to obtain a desired film thickness in the insulating film 32b, the viscosity of the coating liquid, the surface tension, the rotation speed of the spin coat, and the rotation time are determined, and an allowable semiconductor is determined based on these conditions. Determine the maximum size of the membrane. Specifically, the sizes W1 and W2 of one side of the semiconductor film 31 are set to 50 μm or less, and according to this, two semiconductor films 31 are patterned in one pixel. Thus, by forming the semiconductor film into a plurality of parts in one pixel, the required performance of the transistor can be satisfied as a whole while reducing the size of each semiconductor film 31.
[0030]
Next, a method for manufacturing a transistor using one of the semiconductor films 31 shown in FIG. 4 will be described with reference to FIGS. 5 and 6 are diagrams showing a part of FIG. 4 taken out to a different scale, and a part of the substrate 10 in each step corresponds to the cross-sectional view of the liquid crystal display device shown in FIG. It shows.
[0031]
When the patterning of the semiconductor film 310 is completed, as shown in FIG. 5A, the substrate is irradiated with UV light in an oxygen-containing gas atmosphere to decompose and remove contaminants (such as organic substances) present on the substrate surface. Here, as the UV light to be irradiated, a low-pressure mercury lamp having a peak intensity at a wavelength of 254 nm or an excimer lamp having a peak intensity at a wavelength of 172 nm is used. The light in this wavelength range is oxygen molecules (O ₂ ) Ozone (O ₃ ), And this ozone is further converted into oxygen radicals (O ^* Therefore, organic substances adhering to the substrate surface can be efficiently removed by using the highly active ozone and oxygen radicals generated in this manner.
[0032]
Next, as shown in FIG. 5B, the substrate is heated to 200 ° C. to 500 ° C., and the substrate is irradiated with UV light in an oxygen-containing gas atmosphere, and oxygen radicals (O ^* ). Then, the surface of the semiconductor film 31 is oxidized by oxygen radicals to form a silicon oxide film (second insulating film) 32a (second insulating film forming step). The UV light to be irradiated has a peak with a wavelength of 254 nm or less. As described above, light in this wavelength region is oxygen molecules (O ₂ ) Ozone (O ₃ ) And this ozone is further converted into oxygen radicals (O ^* ). In addition, light having a wavelength of 175 nm or less emits oxygen molecules (O ₂ ) Directly, and oxygen radicals (O ^* ) Is generated. Then, such active oxygen radicals are generated on the surface of the substrate heated to a high temperature, whereby the surface of the semiconductor film 31 is oxidized and an insulating film 32a is formed.
[0033]
Here, the light source that emits the UV light may be any light source that can emit light having the above-described wavelength component. For example, a light source having a plurality of line spectra such as a low-pressure mercury lamp, an excimer lamp, or an excimer lamp. Those having a monochromatic spectrum such as a laser and those having a continuous spectrum such as a xenon flash lamp are used. Examples of the excimer laser include a krypton fluoride laser having a central wavelength of 248 nm and an argon fluoride laser having a central wavelength of 193 nm.
In addition, the substrate may be heated by a resistance heating method such as a hot plate, or may be heating using the energy of light to be irradiated. When the substrate is heated using light energy, light having a wavelength component suitable for heating the substrate is preferable. By using the energy of the irradiated light to heat the substrate, the efficiency of energy utilization can be improved. That is, the energy of light that has not been used to generate oxygen radicals can be efficiently used for heating the substrate. Further, other heating means using resistance heating or the like is not required, and the apparatus can be simplified. Note that the substrate may be heated by combining the resistance heating method and the light energy heating method.
[0034]
In this process, since oxygen radicals are generated without using plasma, the film surface is less damaged, and a high-quality interface with the semiconductor film 31 can be formed. In addition, this method can simplify the apparatus configuration as compared with the case where oxygen radicals are generated by plasma, and has an advantage that the processing time can be shortened because the space in which the substrate is disposed does not need to be set to a vacuum pressure.
[0035]
Next, as shown in FIG. 5C, a silicon oxide film (first insulating film) 32b is formed on the insulating film 32a (first insulating film forming step). The insulating film 32b is formed by spin-coating a coating solution in which polysilazane is mixed with xylene on a substrate and then performing heat treatment. At this time, the physical properties (viscosity and surface tension) of the coating solution and the conditions for spin coating are those previously determined in the patterning step described above. For example, a coating solution obtained by mixing 10% polysilazane in xylene is spin-coated at a rotation speed of 1500 rpm, and prebaking is performed at a processing temperature of 100 ° C. for 5 minutes. After this, the processing temperature is set to 350 ° C. and WET O ₂ Heat treatment is performed in an atmosphere for 260 minutes. Thereby, a silicon oxide film having a thickness of 150 nm is formed. In this way heat treatment WET O ₂ By performing in an atmosphere, the nitrogen component in the insulating film that causes polarization can be reduced.
[0036]
Next, as shown in FIG. 6A, on the insulating film 32b, doped silicon, a silicide film, aluminum (Al), tantalum (Ta), molybdenum (Mo), titanium (Ti), tungsten ( W), copper (Cu), chromium (Cr), etc., or a gate electrode forming conductive film made of an alloy containing these metals is formed, and then the conductive film is patterned to scan lines 33 and gate electrodes. 33a is formed (step of forming a gate electrode). Note that the gate electrode 33a may be formed using a single-layer conductive film or a stacked structure.
Next, an impurity element is doped using the gate electrode 33a as a mask. As a result, the source part 31b and the drain part 31c are formed in the semiconductor film 31 in a self-aligned manner with respect to the gate electrode 33a. A region covered with the gate electrode 33a and not doped with impurities becomes the channel portion 31a.
[0037]
Next, as shown in FIG. 6B, the interlayer insulating film 12 is formed so as to cover the gate insulating film 32 and the gate electrode 33a. As the interlayer insulating film 12, for example, an insulating film containing silicon such as a silicon oxynitride film or a silicon oxide film can be used.
[0038]
Subsequently, as shown in FIG. 6C, a part of the interlayer insulating film 12 is opened, and contact holes 12a and 12b are formed at positions corresponding to the source part 31b and the drain part 31c of the semiconductor film 31, respectively. Next, a metal film such as an aluminum film, a chromium film or a tantalum film is formed so as to cover the inner walls of the contact holes 12a and 12b, and a source electrode (signal line) 34 and a drain electrode (intermediate layer) 35 are formed by patterning. Form.
Through the above steps, the transistor 30 is manufactured.
[0039]
Thus, in this embodiment, since the insulating film 32b is a coating film, the unevenness on the substrate generated in the semiconductor film patterning step can be planarized by the insulating film 32b. Thereby, the film thickness uniformity of the gate insulating film 32 is increased, and a transistor having a high breakdown voltage and a small leakage current is obtained. In particular, in the present embodiment, in consideration of the influence of the size of the semiconductor film 31 on the flatness of the coating film, the pattern size is limited within a certain range in the semiconductor film patterning process in advance. Can be made more uniform.
In this embodiment, since the gate insulating film 32 is a laminated film of the insulating film 32 b as the coating film and the insulating film 32 a that is the surface oxide film of the semiconductor film 31, the gate insulating film 32 is excellent between the semiconductor film 31. Interfacial properties are obtained.
[0040]
[Electronics]
Next, specific examples of an electronic device including the liquid crystal device of the present invention will be described.
FIG. 7 is a perspective view showing an example of a portable information processing apparatus such as a word processor or a personal computer. In FIG. 8, reference numeral 1200 denotes an information processing apparatus, reference numeral 1202 denotes an input unit such as a keyboard, reference numeral 1204 denotes an information processing apparatus body, and reference numeral 1206 denotes a display unit using the above-described liquid crystal device.
Since the electronic device shown in FIG. 7 includes a display unit using the liquid crystal device of the above embodiment, high-quality display is possible by reliable switching.
[0041]
In addition, this invention is not limited to the above-mentioned embodiment, It can implement in various deformation | transformation in the range which does not deviate from the meaning of this invention.
For example, in the above embodiment, the gate insulating film 32 has a two-layer structure of the surface oxide film 32a of the semiconductor film 31 and the insulating film 32b that is a coating film, but this may be a multilayer film of three or more layers. . For example, the third insulating film is formed at the interface with the gate electrode 33a by vapor deposition or the like, whereby the electrical characteristics of the transistor can be further stabilized. Of course, when good interface characteristics can be obtained only by the first insulating film 32b, the second insulating film 32a and the third insulating film described above are omitted, and the gate insulating film 32 is made of only the insulating film 32b. A single-layer structure is also possible.
[0042]
4 shows an example in which the semiconductor film is divided into two parts within one pixel, the semiconductor film may be divided into three or more instead. Of course, when the entire size of the semiconductor film determined in step S2 in FIG. 2 is sufficiently small, the semiconductor film can be provided alone without being divided.
In the above embodiment, the liquid crystal device has been described as an example of the electro-optical device. However, the present invention is applied to various devices such as an organic EL display device and an electrophoretic display device. Can do.
[Brief description of the drawings]
FIG. 1 is a diagram showing a main structure of a liquid crystal device according to an embodiment of the invention.
FIG. 2 is a flowchart for explaining a manufacturing procedure of a transistor.
FIG. 3 is a process diagram for describing a method for manufacturing a transistor of the present invention.
FIG. 4 is a process diagram following FIG. 3;
FIG. 5 is a process diagram following FIG. 4;
FIG. 6 is a process diagram following FIG. 5;
FIG. 7 illustrates an example of an electronic device of the invention.
FIG. 8 is a diagram for explaining the influence of the size of a semiconductor film on the film thickness uniformity of a gate insulating film;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Liquid crystal device (electro-optical device), 10A ... Substrate, 31 ... Semiconductor film, 32 ... Gate insulating film, 32a ... Second insulating film, 32b ... First insulating film, 33a ... Gate electrodes, 1200 ... Electronic equipment

Claims (9)

Forming a semiconductor film on the substrate; patterning the semiconductor film in an island shape; forming a gate insulating film on the semiconductor film; and forming a gate electrode on the gate insulating film. A process,
The step of forming the gate insulating film includes a step of forming a first insulating film constituting at least a part of the gate insulating film by a coating method. In the patterning step of the semiconductor film, the step of forming the first insulating film A method for manufacturing a transistor, characterized in that a pattern size of the semiconductor film is set in accordance with physical properties of a coating liquid used in a forming step, coating conditions, and a required thickness of the first insulating film.   In the semiconductor patterning step, an allowable semiconductor film is formed according to the physical properties of the coating liquid used in the first insulating film forming step, the coating conditions, and the required thickness of the first insulating film. In addition to determining the maximum size, the total size of the semiconductor film is obtained based on the required performance of the transistor. If the total size is larger than the maximum size, the semiconductor film is divided into a plurality of parts, 2. The method of manufacturing a transistor according to claim 1, wherein the size of the semiconductor film is not more than the maximum size.   3. The method for manufacturing a transistor according to claim 1, wherein the step of forming the first insulating film is performed by a spin coating method.   4. The method according to claim 1, wherein the forming step of the first insulating film is performed by applying polysilazane on the semiconductor film and converting it into silicon oxide by heat treatment. The manufacturing method of the transistor of description. The method for manufacturing a transistor according to claim 4, wherein the heat treatment is performed in a WET O ₂ atmosphere.   The step of forming the gate insulating film includes a step of forming a second insulating film constituting a part of the gate insulating film by subjecting the semiconductor film to surface oxidation before the step of forming the first insulating film. The method for producing a transistor according to claim 1, wherein:   The method for manufacturing a transistor according to claim 6, wherein the forming step of the second insulating film is performed by performing plasma processing on a surface of the semiconductor film using an oxygen-containing gas as a processing gas.   7. The method for manufacturing a transistor according to claim 6, wherein the step of forming the second insulating film is performed by irradiating the semiconductor film with ultraviolet rays in an oxygen-containing gas atmosphere.   The step of forming the gate insulating film includes a step of forming a second insulating film constituting a part of the gate insulating film by an evaporation method at an interface with the semiconductor film or an interface with the gate electrode. The method for producing a transistor according to claim 1, wherein the transistor is a transistor.

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